Because the EU has a very different reaction pattern and overall resources. It was never a question about downing ships that are sabotaging cables.

Neither the EU countries, nor the US have enough ships to patrol or escort every civilian ship that happens to parse over an undersea cable.

Assume that the Russian shadow fleet starts targetting US cables. What would, could, the US do? The US government could easily retaliate by simply opening the US weapons depos to the Ukrainians. Target US infrastructure and Ukraine gets whatever it wants. The EU can't really do something similar.

Technically you're not wrong, if the EU navies where large enough, they could just escort every single civilian ship, but that's not realistic.

its not about hard power necessarily, but soft power. If the EU united politically and made these harassment attacks consequential then they would stop.

E.g. perhaps something along the lines of prison for captains who were 'derelict in duty', rewards to crews who grass and seizing ships that, by dragging anchors 'by accident', have proven themselves unseaworthy etc.

I believe something like this will happen, sooner or later. For now, it's not easily to organize as the crew can always use the excuse "oh, this was unintentional" but charging them with the cost of repair plus additional penalty could be a good starting point.

> but charging them with the cost of repair plus additional penalty could be a good starting point.

Good luck enforcing that. The "shadow fleet" ships all operate under flags of convenience and ownership is hidden behind layers upon layers of shell companies.

If the fines and damages are not paid then perhaps the ship and its cargo are liquidated?

The problem is, the oil tankers are single wall, shoddily maintained, probably contaminated with all sorts of nasty stuff and with barely any history records. These things are effectively floating time bombs - assuming you can find a buyer for the seized cargo given the lack of paperwork in the first place, you need to sell the ship for scrap because it's nowhere near seaworthy (remember: single wall, no Western insurer will handle that), and that costs a loooot of money if you are a Western country and can't just haul it off to Alang [1] or whatever place and let others deal with the fallout.

[1] https://www.bbc.com/news/uk-56196069